Assessment of left ventricular volume by an ambulatory radionuclide monitoring system during head-up tilt in patients with unexplained syncope: relation to autonomic activity assessed by heart rate variability.
J Nucl Cardiol
; 8(6): 660-8, 2001.
Article
in En
| MEDLINE
| ID: mdl-11725262
ABSTRACT
BACKGROUND:
Decreased left ventricular volume during head-up tilt plays an important role in triggering syncope in patients with neurally mediated syncope. However, precise changes in left ventricular volume during head-up tilt have not been well investigated. This study was conducted to test the hypothesis that the decline in left ventricular volume during tilt could trigger ventricular mechanoreceptor activation. METHODS ANDRESULTS:
To investigate the mechanisms of tilt-induced syncope, we measured the temporal changes in left ventricular volume, ejection fraction, cardiac output, and heart rate variability indices during head-up tilt in 25 patients with syncope of undetermined etiology. Eleven patients had a cardioinhibitory response (CI group), 7 patients showed a vasodepressor response (VD group), and 7 patients demonstrated a negative response (NG group). Before syncope, ejection fraction increased most in the CI group, the left ventricular end-diastolic volume declined most in the VD group (VD group, -11.0% +/- 3.3%; CI group, -2.8% +/- 4.8%; NG group, -3.4% +/- 2.2%; P <.005), and the high-frequency spectra increased most in the CI group (CI group, 25.0% +/- 21.0%; VD group, -4.1% +/- 11.7%; NG group, -5.3% +/- 12.7%; P <.01). The vasodepressor response was dependent on left ventricular volume, whereas the cardioinhibitory response was related to the vagal activity reflected by high-frequency spectra.CONCLUSIONS:
The precise evaluation of left ventricular volume by an ambulatory radionuclide monitoring system combined with a heart rate variability analysis is considered useful for clarifying the pathophysiology of neurally mediated syncope.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Posture
/
Autonomic Nervous System Diseases
/
Syncope
/
Cardiac Volume
/
Electrocardiography, Ambulatory
/
Ventricular Dysfunction, Left
/
Heart Rate
Type of study:
Etiology_studies
Limits:
Adult
/
Female
/
Humans
/
Male
Language:
En
Journal:
J Nucl Cardiol
Year:
2001
Document type:
Article